The invention relates to a method for sintering and pressing ceramic compacts which contain voids and are moved in the form of bars lengthwise through a heating apparatus by which a limited high-temperature zone is produced in the compact, in which the compact is heated above its sintering temperature and is condensed with reduction of bulk to a sintered body.
Such a method is known and has been used for the transformation of compacts of shaped silicon dioxide--so-called "greenware"--to sintered bodies of silicon dioxide. The compact is relatively soft and difficult to handle, while the finished body is virtually clear as glass and very strong. In the sintering process a marked reduction of volume occurs through a flowing action which results in mechanical instability of the sintering process. With the compact lengths of about 200 cm and the diameter of about 20 cm commonly employed heretofore, it frequently happened that the sintered rods were bent and/or irregular in diameter, thereby making the further working of these pieces difficult or at least less profitable.
It is therefore the object of the invention to eliminate the mechanical instabilities in the sintering process in regard to their effect on the end product, and to offer a manufacturing process of the kind described above whereby sintered compacts can be achieved without difficulty, in which the rod axis will be rectilinear.